It is well known to form the wall of a container from a plastic laminate which includes a layer of plastic and a layer of fluid impermeable material, such as aluminum foil. Such a container may be formed from extruding a sleeve of plastic, such as polypropylene. Typically, a laminate of aluminum foil and the same plastic material is laminated to the extruded plastic sleeve. It is also well known to form the bottom closure of the container by extrusion molding and to provide such a bottom closure with a layer of fluid impermeable material. Typically, the bottom closure is then sealed to the container sleeve as a last step in the manufacturing process. The aforedescribed construction of the container sleeve and bottom closure provides excellent characteristics with respect to fluid impermeability. However, a closure for such a container is required which does not jeopardize the fluid impermeability of the container, but the closure must still function to removably seal the container and the product contained therein. In addition to having such characteristics, the closure must also be relatively easy to open.
With regard to such closures for these types of packages, it is also known to construct same by attaching a sealing member to the inside surface of a cover. Typically, this may be done by laminating the sealing member, which may consist of a layer of aluminum foil disposed between two layers of plastic, to the inside surface of a plastic cover. The cover may also be provided with a center portion which is countersunk and is surrounded by a downwardly-extending groove which is substantially U-shape in cross section, so that the top edge of the container walls enter the U-shaped groove. Typically, a sealing member extends into the U-shaped groove and is sealed to the cover and the container walls. Such an arrangement typically provides a good, fluid-impermeable seal. However, in order to open the closure and penetrate the sealing member, a gripping member is typically formed as part of the cover and is provided with a tip which penetrates the sealing member and permits the tearing off of the center portion of the cover along a tearing strip. However, such an arrangement does not always provide a smooth transition between the container and the portions of the closure which remain attached to the container.
Accordingly, it is an object of the present invention to provide an improved closure which overcomes the aforesaid problem. Specifically, it is within the contemplation of the present invention to provide an improved closure for a container opening which provides a fluid-impermeable seal and which requires only one operation to remove the cover from the container and form an opening in the sealing member.